1. Field of the Invention
This invention relates to a wood-planing machine, more particularly to a thickness-indicating device for a wood-planing machine, which indicates the thickness of a workpiece to be cut.
2. Description of the Related Art
Referring to FIGS. 1, 2 and 3, a conventional wood-planing machine is shown to include a machine bed 1 (only a portion thereof is shown in FIG. 1), and a cutter seat 2 disposed vertically and movably on the machine bed 1. A thickness-indicating device 10 includes a rotatable pointer 11, a reed spring 12 fixed on the cutter seat 2, and a scale member 13. When it is desired to cut a workpiece 100 that is held on the machine, the cutter seat 2 is moved toward the workpiece 100. During downward movement of the cutter seat 2, a curved end 121 of the reed spring 12 presses against the workpiece 100 so as to deform, thereby pushing upward a nose 112 of the pointer 11. A free end 111 of the pointer 11 is thus turned upward, thereby indicating the thickness of the workpiece 100 to be cut. The conventional thickness-indicating device 10 suffers from the following disadvantage:
(1) A linear contact is present between the reed spring 12 and the workpiece 100, thereby hindering smooth movement of the workpiece 100 between the reed spring 12 and the machine bed 1, which is performed in order to change the portion of the top surface of the workpiece 100 to be cut.
(2) Because the engaging surface area between the reed spring 12 and the workpiece 100 is relatively large, and because the vibration resulting from cutting of the workpiece 100 is transmitted to the reed spring 12, the reed spring 12 easily experiences spring fatigue.
(3) Due to the linear engagement between the reed spring 12 and the workpiece 100, there is a need to exert a relatively large force to depress the cutter seat 2 for deforming the curved end 121 of the reed spring 12. In a case where the workpiece 100 has a somewhat soft top surface to be cut, a shallow slot (not shown) will be formed in the soft top surface. As such, it is difficult for the pointer 11 to indicate accurately the thickness of the workpiece 100 to be cut. Furthermore, the engagement between the curved end 121 of the reed spring 12 and the shallow slot will prevent movement of the workpiece 100 between the reed spring 12 and the machine bed 1.